JPS59204429A - Power source control circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a power supply control circuit that appropriately supplies power to the load of the secondary battery and the equipment in equipment that uses a secondary battery and an external power source as power sources. It is.

<Prior Art> Generally, in devices that use a secondary battery and an AC adapter as power sources, the device can be used while carrying the device using the secondary battery and using the AC adapter in a place where an AC power source is available. When the secondary battery is discharged, it is charged using the AC adapter, but the secondary battery is removed from the device and charged using a dedicated charger, in preparation for portable use.

The former charging method involves connecting an AC adapter to the device and charging the secondary battery installed inside the device.
When the device is in operation, trickle charging is performed, which requires a long charging time. Furthermore, even when the device is not in operation, the charging time is not significantly reduced.

The latter charging method has the problem that the secondary battery must be removed from the device body each time it is charged, which reduces the portability advantage of portable devices by half.

Furthermore, according to the conventional trickle charging method, depending on the discharge state of the secondary battery, too much charging current flows, which not only prevents current from being supplied to the load, but also poses a risk of overloading the AC adapter and damaging the AC adapter. In order to prevent this, the AC adapter must have a large margin in current capacity, resulting in an increase in size. Another method is to incorporate an overcurrent prevention circuit without leaving a margin in the current capacity of the AC adapter, but if the charging current to the secondary battery is large, the current that can be supplied to the load is lower than usual. There is also the problem that the overcurrent prevention circuit is activated at this stage.

<Object of the present invention> The object of the present invention is to eliminate the conventional drawbacks of description,
In particular, it is possible to selectively perform forced charging and trickle charging while the secondary battery is installed in the device body, and to charge the secondary battery appropriately regardless of the discharge state of the secondary battery to be charged.
This also ensures that current is supplied to the load without any problems.

<Description of the principle structure> FIG. 1 is a block diagram of a device having a power supply control circuit according to the present invention.

In the figure, 1 is the commercial AC power supply, 2 is the device itself, and 3 is the A
It is a C adapter. 4 is a constant voltage circuit, and 5 is a gate that switches according to an output control signal. 5 and 7
If both are on, the voltage supplied to the device from the AC adapter is made constant by 4 and supplied to the load 6. A secondary battery 8 is charged by the output voltage of the voltage regulating circuit 4. A control circuit 9 controls the gate 7 and the reference voltage switching circuit 11 according to the state of the mode switch 10. When the mode switch 10 is in the forced charging mode, the gate 7 is turned off, and the reference voltage switching circuit 11 is controlled to apply a low reference voltage to the constant voltage circuit 4. As a result, the power supply to the load 6 is cut off regardless of the state of the power switch 5, and the voltage regulating circuit 4 outputs a higher voltage than usual. Therefore, 4
All of the current output from the secondary battery 8 becomes a charging current for the secondary battery 8, and charging is completed in a short time. When the mode switch 10 is in the normal mode, the gate 7 is turned on and the reference voltage switching circuit 11 is controlled to apply the normal reference voltage to the voltage regulating circuit 4. As a result, power is supplied or cut off to the load 6 depending on the state of the power switch 5, and the voltage regulating circuit 4 outputs a normal voltage. Therefore, the current output from 4 trickle charges the secondary battery.

Note that 12 is a break signal generated from inside the device, and when this signal is generated, 9 turns off the gate 7, thereby turning off the power regardless of the state of the switch 5. 13 is a signal output from the over-discharge detection circuit of the secondary battery, and 9 also turns off the gate 7 based on this signal.

FIG. 2 is a diagram showing a specific example of the circuit.

14 is a constant voltage control circuit using one chopper type;
The voltage V* inputted from the AC adapter is made constant by the switching of the TRI.

Reference numeral 14 denotes a circuit that performs switching control of this transistor TRI, and uses the potential at the 0 point as a reference voltage to make it a constant voltage. 18 is a DC-DC converter, and 17 is another excitation oscillation circuit. VOI, VO2, and VO3 are converter outputs. This oscillation circuit 17 oscillates when TR7 is on, and stops oscillating when TR7 is off. TR7 corresponds to gate 7 shown in FIG. 1, but power is supplied to converter 18 from point d, and TR7 only controls oscillation of oscillation circuit 17.

When the mode switch 10 is on the a side, the forced charging mode is entered. That is, when the mode switch 10 is on the a side, the base potential of TR3 increases and TR3 is turned on. Therefore, the potential at point 0 decreases, and the control circuit 14 generates a voltage at point e higher than normal (performs TRI switching control).

16 is a circuit that detects the voltage of the secondary battery or the voltage at point e, and detects the over-discharge state of the secondary battery or the fact that the switch 10 is on the a side.

When the mode switch 10 is on the a side, 16 lowers the base voltage of TR4. Therefore, TR4 is turned off, and TR5, TR6, and TR7 are accordingly turned off. As a result, the power supply to the main body of the device is cut off regardless of the state of the switch 5.

If the mode switch IO is on the b side, the base voltage of TR3 decreases and TR3 is turned off. Therefore, the potential at the 0 point -
This becomes the normal reference voltage. As a result, the control circuit 14
controls the switching of TRI so that a normal voltage is applied to point e. On the other hand, 16 detects that a normal voltage is being supplied to point e and turns on TR4. Usually 12
Since the break signal of is at GND potential, this causes T
R5°TR6 and TR7 are each turned on. Therefore, when the switch 5 is turned on, power is supplied to the device. Note that even if the mode switch 10 is on the b side, if the voltage of the secondary battery is below a predetermined value, ]6 detects this and as a result, T R,
Turn off 7. The signal output from 16 in this case corresponds to signal 13 shown in FIG.

15 is a circuit that detects that the charging current of the secondary battery has fallen below a predetermined value. Specifically, the circuit 15 detects that the potential at point f has become below a predetermined value, and turns on TR2. Therefore, even if the mode switch IO is on the a side (forced charging mode) and TR3 is on, TR2
By turning on, TR3 is turned off, and point C becomes the potential in the normal mode. Therefore, even if the battery is left in forced charging mode, forced charging will be canceled when charging of the secondary battery is completed.

Note that TH is a thermistor for controlling the reference voltage at point C according to the ambient temperature.

<Other Embodiments> FIG. 3 shows an example in which the power supply circuit shown in FIG. 1 is more effectively controlled in two modes. The difference from FIG. 1 is that a current limiter circuit 19 is inserted into the output of the constant voltage circuit 4, so that the current limiter circuit 19 is inserted into the output of the constant voltage circuit 4.

Now, when the mode switch 10 is in the normal mode, a normal constant voltage is output from 4, and the secondary battery 8 is trickle charged. At this time, the limiter 20 is enabled by the signal output from 9.

Therefore, if the charging current reaches a predetermined value, the IJ emitter is activated and the charging current is limited.

FIG. 4(1) shows the current-voltage characteristics of the constant voltage circuit 4 in the normal mode. If the charging current is 13 or more, limiter 2
0 is activated. On the other hand, the limiter 19 operates at a current of 11 or more. For example, if the device is used in normal mode with the secondary battery still in a severely discharged state, the charging current of the secondary battery becomes 13 or more and the limiter 20 is activated. if,
Without the limiter 20, the current output from the constant voltage circuit 4, that is, the sum of the charging current and the current flowing to the load 6, is 1 month.
If the battery voltage exceeds the limiter 19, the limiter 19 will be activated, and not only will charging not be possible, but the device will not be able to be used.

Furthermore, if there is no limiter 19, there is a risk that an overcurrent exceeding the rated value will flow through the AC adapter 3.

When the mode switch 10 is in forced charging mode, 9' controls the voltage switching circuit 11, turns off the gate 7, and disables the limiter 20 so that the forced charging voltage is output from the constant voltage circuit 4. do. Therefore, the charging current can flow 13 or more.

FIG. 4 (2) shows the characteristics in the forced charging mode. Furthermore, when the charging current becomes low and becomes less than 2, the signal 13 is generated as in the above implementation, and the output voltage of the constant voltage circuit 4 becomes the trickle charging voltage. ■Becomes 1.

<Effects> As described above, according to the present invention, a secondary battery can be charged in a mode according to necessity.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a device having the principle power supply control circuit of the present invention, Fig. 2 is a diagram showing a specific circuit example of Fig. 1, and Fig. 3 is a diagram showing a specific example of the circuit shown in Fig. 1.
The figure shows another embodiment, and FIG. 4 is a diagram showing the operating characteristics of FIG. 3. 1 Commercial AC power supply, 2: Equipment body, 3: AC adapter, 4 Constant voltage circuit, 5: Power switch, 6 Load, 7-
Gate, 8; secondary battery.

Claims (1)

[Claims] 1. For products powered by secondary batteries and external power sources,
It is possible to selectively switch between a mode in which the power supply to the load is effectively cut off and the secondary battery is forcibly charged by an external power supply, and a mode in which the secondary battery is trickle charged while supplying power to the load. A power supply control circuit featuring: